In making chain it is conventional to utilize apparatus which automatically forms links from a straight strand of wire of a selected diameter ranging anywhere from 0.003 inch to 0.250 or more. The wire is fed into the machine, bent into a single loop having a generally spiral configuration, severed from the straight strand, bent to close the link in a generally circular configuration, then positioned so that the strand of wire which is advanced is threaded through the closed link. The cycle is repeated to form a selected length of chain. The chain links are formed with butt or biased ends which are either in physical engagement with one another or separated by a few thousandths of an inch or more. Conventionally the chain links are then subjected to a soldering operation to ensure the finished product is sufficiently strong for its intended purpose. The soldering operation involves packing the chain to mask and protect it while the chain is subjected to elevated temperatures in a soldering furnace. The wire employed for the chain is either solder cored wire or solder powder must be separately placed between each link joint to prepare it for soldering. In any event, the labor content in manufacturing such chain is significantly increased due to the requirement of the soldering operation, the yield is decreased due to links being deformed during handling; materials cost are increased due to the requirement of solder and masking materials and capital equipment expenses are increased due to the furnaces as well as energy costs for operating such furnaces.
In copending application Ser. No. 229,553 referenced above, apparatus and methods of welding separate links of wire of the same type as that used in making chain is disclosed and claimed. As set forth in that application, a welding head is mounted adjacent a link forming mechanism and is adapted to be moved to and from the link forming work station. A complete cycle for forming and welding a link is initiated by actuating a switch which causes a camming head to descend and bend the distal end portions of two upstanding legs of a generally U-shaped work piece into a closed link. The camming head then ascends and an electrode head moves to the work piece and is positioned a selected distance therefrom. A selected gas is directed to the work area and the atmosphere between the electrode and the work piece is ionized. Once the proper level of ionization is achieved, a welding arc travels from the electrode to the work piece to effect the weld. The electrode head then retracts, the work piece is released and a new work piece is presented at the work station to complete the cycle. This apparatus and method has proven to be very effective in welding wire links providing a good strong joint with minimal marring of the link surface. It is an object of the present invention to adapt the apparatus and method set forth in the referenced application Ser. No. 229,553 to make it suitable for use with existing automatic chain making machines. Another object is the provision of welding apparatus for use with automatic chain making machinery which will obviate conventional soldering operations heretofor used. Another object of the invention is the provision of welding apparatus which is simple, reliable and yet usable with a variety of different types of automatic chain making machinery including machinery in which the chain link is moved to the various operations at the work stations as well as machinery in which the chain link is held stationary and processing elements are brought to it.